The explanation for low-frequency switching noise is usually attributed to the switching of the logic gates in electronic circuits. When these gates switch, they draw more currents This change in current develops a voltage of V=LdI/dt (where L is the inductance, I is the current, and t is the time), for some non-zero inductance always exists, through which extra current must be supplied.
Both the understanding of and the method of modeling delta-I noise has recently been elucidated by Jiayuan Fang et al, in a series of journal publications. Experimental confirmation of the modeling approach has been affirmed by a collaboration between Jiayuan Fang and IBM Microelectronics of Endicott, New York. "A New Approach to Signal Integrity Analysis of High-Speed Packaging" by Yuhze Chen, Zhaoqing Chen, Khonghua Wu, Danwei Xue, and Jiayuan Fang, Proceedings of the 1995 IEEE 4th Topical Meeting on Electrical Performance of Electronic Packaging, pp. 235-238.
In designing high-speed switching and high clock rates for electronic circuits, Fang's insights are important, particularly where the wavelength of the switching noise corresponds to components of the highest frequency, and where it is comparable to, or even smaller than, the dimensions of such circuits. In particular, it has been shown that the previous, low-frequency description or understanding of delta-I noise as LdI/dt is inadequate. Rather, delta-I noise must now be considered as a propagating wave between the conducting planes of the circuit boards.
The present invention has as its objective the reduction of undesirable reflections of power-supply-induced fluctuation signals as they strike the perimeter of a circuit board. These undesirable signals can arise, for example, from current surges in vias supplying power to chips. These signals propagate in a radial-mode waveguide, as suggested by Fang.
This invention also has as its objective the attenuation of such undesirable signals as they propagate to and from the perimeter of the circuit board. Such signals would affect the magnitude of the undesired signal at other vias disposed upon the circuit board.